I do the following:
0) start with a plain-out-of-the-box dual core minnow board with a 2 Amp power 
supply and an HDMI monitor attached.
1) remove all USB and SD modules
2) connect a keyboard and mouse to the top (USB2) slot via a powered hub
3) unplug the power to the minnowboard then re-plug it, and hit F2 many times
Result: there is no response to the keyboard or mouse.  It runs the memory 
check then goes to the UEFI shell (which shows no devices).  I try to type 
“exit” and there is no response.

Variations:
4) Plug the keyboard (without a mouse) directly into the top plug (USB2) and 
repeat.  Again same — no response to the keyboard.
5) Plug the powered hub with keyboard and mouse attached into the bottom (USB3) 
plug.  Same — no response to keyboard.
6) same as above with a USB stick holding Ubuntu installer plugged into the 
powered hub (or directly into the lower slot or even directly into the upper 
slot — with the keyboard plugged into the other slot) — Same.

But:
7) If i insert an SD card with Ubuntu installed on it, and unplug/replug then 
it will boot to Ubuntu (again, no response to the keyboard during UEFI phase).  
Under Ubuntu, the keyboard is live — just as normal for Linux.

And:
With Ubuntu running, I can tell Ubuntu to reboot.  And (lo and behold!) if I 
hit the F2 key while it is rebooting the keyboard is live and I get dropped 
into the BIOS boot menu.  I can then use the keyboard to choose to boot from 
either the Ubuntu SD card or a USB stick with the Ubuntu installer, or anything 
else I might wish.  Magic!


So…  I’m guessing that Ubuntu does some kind of initialization on the USB 
hardware that survives the reboot as long as the power is not removed.  But 
unplugging the power causes that initialization state to be reset and the 
keyboard goes inactive until the next time it boots into Ubuntu.

It’s starting to sound like a firmware bug…
If so, I’ll be happy to work with the engineers to debug it and test a fixed 
firmware version.

Enjoy!
Rick

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